Note: this page is updated continuously, and more information will be added.
Artists and clients shouldn't have to pay for access to each other, only for work done. The platform is currently in beta, however, features for premium accounts are planned. There will always be a free account option.
Currently, ArtStack is only a management platform. You will have to work out payment details just as you've always done. In the future, there may be an option for ArtStack to process payments, for a fee.
Because ArtStack is not a payment processor, you will have to resolve disputes on your own. Someday, artists may be given the option to use escrow for a fee, but it is not possible yet.
For the time being, yes, but currency conversions may be possible in the future.